This invention relates to dermatologic chemical peels prepared from alpha hydroxy acids (“AHAs”). Chemical peels have been used for centuries to improve personal appearance and rejuvenate the skin. Chemical peels exfoliate the skin to remove dead skin cells from the surface of the skin and to expose fresh skin cells, facilitating new growth and a more youthful look. One of the earlier such peels was created from sour milk, which contains the AHA lactic acid. Modern chemical peels typically use glycolic acid, or to a lesser extent, lactic acid, as the primary active AHA. The skin care industry documents significant improvement in characteristics associated with acne, age spots, wrinkles, photo-damage and other age-related skin changes, and numerous other skin conditions. AHAs support a world-wide multi-billion dollar anti-aging skin products industry.
Established industry practice has typically been to provide dermatologic peels in two broad categories, professional strength and consumer products. Professional strength peels include a higher concentration of acid than over-the-counter consumer retail products, are designed for occasional use, and normally are administered in controlled conditions by an individual trained to do so. For example, a professional strength face peel may be applied by a therapist at a resort health spa or in a salon setting or physician's office. A typical professional glycolic acid peel treatment is applied at an acid concentration of from about 20% to 35% by weight at a pH of approximately 3.0 for a period of about three to five minutes. The therapist then deactivates the peel with a buffer solution, typically sodium bicarbonate, which neutralizes the acid, or rinses the skin liberally with water to remove the acid and to bring the acid condition of the skin to a pH level similar to normal skin. The therapist usually monitors individual perceptions of redness, stinging, or pain and blistering and can end the treatment, if necessary, based on these perceptions.
On the other hand, consumer products intended for home use or other uncontrolled settings normally include a concentration of acid sufficiently low to reduce the possibility of negative effects, even if the consumer uses the peel frequently or does not rinse it off. Thus, consumer products may compromise efficacy for a degree of control inherent in application of a low acid formulation sufficient to preclude overexposure. A typical consumer grade glycolic acid peel contains acid at a concentration of about 10% or less and is applied at a pH of 3.5 or more. Although the pH is acid, the concentration of acid in solution is dilute to reduce the chance of redness, stinging or blistering, even if the consumer does not rinse.
It would be desirable to improve acid peels and to provide acid peels that can achieve better or at least equivalent results than those now available and with less intervention required, while at the same time avoiding the likelihood of redness, stinging, burning, or blistering caused by excessive exposure to the low pH of professional strength peel formulations.